(300-41) Sorghum accessions varying in phosphorus acquisition efficiency adopt an ‘outsourcing strategy’ via arbuscular mycorrhizal fungi for efficient P uptake
Graduate Research Assistant Clemson University Central, South Carolina
Body of Abstract: Phosphorus (P), an essential macronutrient for plants, is distributed non-uniformly in the soil due to its strong sorption and low mobility. Plants respond to P-limitation by modifying the P-acquisition strategies, such as increasing soil exploration by root proliferation, root exudation, and forming a symbiosis with Arbuscular Mycorrhizal Fungi (AMF). During P-limitation, plants tend to tradeoff one strategy over another to reduce carbon cost and enhance the efficiency of acquiring P. The objective of our study was to understand the tradeoffs among P-acquisition strategies of P-efficient and inefficient sorghum accessions under AMF symbiosis and heterogenous distribution of P. We hypothesized that AMF-induced root morphological plasticity and root metabolite profiles would vary differentially between P-efficient and P-inefficient accessions. We also hypothesized that the spatial heterogeneity of soil phosphorus would influence the root plasticity of the P-efficient and P-inefficient accessions.
We tested our hypothesis under greenhouse conditions using various accessions of Sorghum bicolor that differ in root architecture traits. These accessions were supplied with iron phosphate (uniform and patch) and mycorrhiza (AMF and non-inoculated control; NAM) treatments. Our results revealed that plants colonized with AMF had higher shoot biomass and tissue P content than non-mycorrhizal plants. The lower specific root length (SRL) in AMF treatment than NAM, irrespective of accessions, indicated that in the presence of AMF, plants adopted an ‘outsourcing strategy’ to acquire P. Patch treatment also had lower SRL and higher tissue density than uniform treatment, indicating reduced root production. The root primary and specialized metabolite profiles also reflected the above P uptake strategy where AMF inoculated plants had a higher abundance of organic acids and specialized metabolites for supporting a functional plant-AMF symbiosis compared to non-inoculated control plants. Our results emphasize that enhancing the AMF symbiotic efficiency in agroecosystems can improve P-acquisition in sorghum accessions varying in P uptake efficiency.